This is a divisional application of U.S. Ser. No. 09/823,542 filed on Mar. 30, 2001 and which is a continuation of International application PCT/EP99/07263 filed Oct. 1, 1999, which claims priority under 35 U.S.C. §§ 119 and/or 365 to patent application Serial No. 98/12594 filed in France on Oct. 3, 1998, the entire content of which is hereby incorporated by reference.
The invention concerns the crowns of tires and, notably, the rubber decouplings placed between the reinforcing plies of those crowns.
The crowns of tires usually comprise a carcass reinforcement, a belt reinforcement with usually at least two superposed reinforcing plies formed by cords parallel in each ply and criss-crossed from one ply to the other and a tread.
The crowns of tires are in contact with the road and must transmit to the wheel, by means of the sidewalls and beads, the transverse stresses necessary to steer the vehicles. For the road performance of vehicles to be satisfactory, it is necessary for the crowns to be very rigid relative, for example, to the sidewalls. A permanent objective is to try to obtain such high rigidity as simply and economically as possible.
It is well known that the rubber decouplings of belt reinforcing cords contribute to obtaining high rigidity. That is why those rubber decouplings usually have a high modulus of elasticity. On the other hand, the rubber decouplings in contact with the cords of carcass reinforcements usually have a low modulus of elasticity because they must withstand without damage the high deformations they undergo in the sidewalls of the tires.
On the other hand, a great deal of research is being conducted to reduce the gasoline consumption of road vehicles. For that purpose, emphasis is on the design of tires having a very low rolling resistance, while maintaining the other properties of wear, adherence, performance, etc., as economically as possible.